This invention relates to chirp spread-spectrum communication systems, and in particular to such systems used on noisy network media, such as power lines.
Spread spectrum communication is a method whereby information is communicated using a bandwidth that greatly exceeds that required by information theory. Since these methods provide their signals over a wide bandwidth, they may be immune to large amounts of noise within that bandwidth. In chirp spread-spectrum method, a signal burst known as a chirp is transmitted. Each chirp has energy spread across a frequency range. The frequency spread may be achieve by frequency sweeping or other known techniques (such a direct sequence). The chirps may be sent in succession and modulated with information to be communicated to a receiver. A filter in the receiver is matched to the chirp, enabling a chirp to be detected in the presence of noise (a term which we use collectively to refer to all impairments to the communications channel).
My U.S. Pat. No. 5,090,024, entitled SPREAD-SPECTRUM COMMUNICATIONS SYSTEM FOR NETWORKS, issued Feb. 18, 1992, is herein incorporated by reference. The patent describes a system for communicating over power lines, and the like, that employs chirp spread-spectrum communication techniques.
In a communication network, several transmitters and receivers may communicate with each other over a network medium. In certain networks, collision (or contention) resolution strategies are implemented to resolve situations in which two or more transmitters simultaneously require use of the network medium.